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Researchers have found that prenatal factors and childhood experiences, including birth weight, diet and exercise patterns, migh

admin2009-06-24  18
问题     Researchers have found that prenatal factors and childhood experiences, including birth weight, diet and exercise patterns, might affect a woman’s risk of developing breast cancer.
    Evidence is accumulating, though the research is still in its very early phases, that the periods before and soon after birth, childhood and early adolescence are much more important to breast cancer risk than had been appreciated. Just as heart disease has its origins in childhood, breast cancer is not just an adult disease. For example, there is a strong link between high-fat diets in the population and high rates of breast cancer, but at best a weak relationship to the amount of fat an individual woman consumes as an adult. But the effects of fat in a child’s diet may explain why Japanese women who emigrate to the United States maintain their low risk of breast cancer, while the risk faced by their American-born daughters and granddaughters approaches that of white American women.
    Studies suggested that breast cancer risk might in part be determined by the kind of diet a woman consumed as a child and even what her mother ate during pregnancy—if the diets were high in calories, and especially if they were rich in animal fat.
    Animal studies have also suggested that a prenatal diet rich in polyunsaturated fats, which include most vegetable oils, can increase the susceptibility of fetal breast tissue to the cancer-stimulation effects of estrogen. Several studies in adults have indicated that mono-unsaturated fats like olive or canola oil are protective. The high-calorie diet typically consumed by Americans, for instance, fosters the production of estrogens associated with early puberty and early menarche, both of which are already linked to breast cancer risk. Studies also show that the effects of diet on breast cancer risk may well start in the womb. Based on data gained, epidemiologists found a clear link between birth weight and later risk of breast cancer: The bigger the baby, the greater the risk. Since a baby’s birth weight is largely determined by how much weight a woman gains during pregnancy.
    Also worrisome is the precipitous rise in childhood obesity and a concurrent decline in physical activity in the United States.
    Nutrition can induce changes in the fraction of estrogens bound to the serum proteins and, therefore, can enhance or decrease the action of estrogens of highly susceptible target organs like a woman’s breasts. Fruits arid vegetables are protective with regard to estrogen stimulation. Animal fat, decreases this binding, and thus increases the amount of estrogen available to stimulate tissue growth.
    Therefore, even small changes in overall intake of estrogenic substances, decreases in animal fat consumption and increases in fruit and vegetable fiber could result in dramatic changes in breast cancer risk later in life.
选项 A、because of Americans’ diet, people there, including immigrants, have a high risk of breast cancer.
B、an adult woman’s intake of high-fat diets has little to do with her risk of breast cancer.
C、American white women have a higher risk of breast cancer than women with darker skins.
D、Asian immigrants’ daughters and granddaughters brought up in the U.S. have a higher risk of breast cancer than their mothers and grandmothers.
答案B
解析
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